This invention relates to a display device, a driving method therefor, and a portable terminal equipment. Particularly, it relates to a display device which uses a liquid crystal cell or an EL (electroluminescence) element as a pixel display element, a driving method therefor, and a portable terminal equipment such as a portable telephone having such a display device mounted thereon.
As a display device for a portable terminal equipment represented by a portable telephone, a liquid crystal display device or an EL display device has been broadly used. In principle, the liquid crystal display device and the EL display device are display devices of low power consumption which do not need large power for driving. Therefore, these display devices are advantageously used in portable terminal equipments.
For example, a liquid display device mounted on a portable telephone may make display in a part of its screen, as a display function of standby mode or the like. Hereinafter, this display mode is referred to as a partial screen display mode. In order to realize such a partial screen display mode for making display in a part of the screen in the standby mode or the like, the liquid crystal display device or the EL display device must carry out a refresh operation using a certain image signal such as a white signal or a black signal, not only in an area for display a target image on the screen but also in a non-display area.
Since the liquid crystal display device or the EL display device must carry out the refresh operation also in the non-display area when realizing the partial screen display mode as described above, a driver circuit for driving pixels must be constantly fully operated even in the standby mode or the like. Therefore, power for this driving is required and reduction in power consumption is made difficult.
In a liquid crystal display device of normally-white display, if black display is made in a non-display area in the partial screen display mode, the charge and discharge current with respect to the device capacitance increases, preventing reduction in power consumption. The same is true of white display made in a non-display area in a liquid crystal display device of normally-black display. Moreover, in the EL display device, if white display is made in a non-display area, a light-emitting current must constantly flow and this also prevents reduction in power consumption.
In view of the foregoing status of the art, it is an object of the present invention to provide a display device which enables realization of a partial display mode with a simple structure and reduction in power consumption, a driving method therefor, and a portable terminal equipment having this display device mounted thereon.
According to the present invention, there is provided a display device which has storage means for storing data of one line and is adapted for making regular image display in a partial area in the direction of row, in a display area having pixels arranged in the form of a matrix, on the basis of the data of one line stored in the storage means and for making specified color display in the remaining area. In the display device, the operation to write data of one line to the storage means is repeatedly carried out for every line during the display period for making regular image display, whereas data of one line is written to the storage means at the beginning of the display period for making specified color display and the data written to the storage means is repeatedly read out during the display period.
With such a structure according to the present invention, during the display period for making regular image display, inputted image data is sequentially stored into the storage means by one line each, and the stored data of one line is sequentially read out from the storage means and supplied as display data of each pixel to the display area. On the other hand, during the display period for making specified color display, color data of one line (for example, white data or black data) is first written to the storage means at the beginning of the display period and then the stored data is held until the display period ends. During this display period, the stored data in the storage means is repeatedly read out and supplied as display data of each pixel to the display area.
The other objects and specific advantages of the present invention will be further clarified from the following description of embodiments.